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Thread: Electricity Costs

  1. #1
    Senior Member robusto's Avatar
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    Electricity Costs

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    Not a controlled scientific experiment by any means, but for those completely in the dark about how much electricity is used to leave
    a machine on this may shed some light.

    The figures are to leave it idling. Actually brewing will alter the figures to take into account the pump etc but given the few coffees brewed daily shouldn't be much higher.

    Machine here is a Grimac Eclisse 2 group.
    Ambient temperature 18į
    Amps: 10.5
    Volts 249
    Power: 2614 watts

    Heating element on: at 0.6 bar
    Heating element off: at 0.8+ bar

    On time: 22 seconds
    off time 2 mins 13 secs

    Per minute power: 43.56 watts
    Per on cycle watts: 15.97 watts

    So every time the element comes on, for 22 seconds, it uses 15.97 watts

    In one hour, the machine will have cycled on/off 23.2 times. In 24 hours, 511 times.
    In one hour, the heater will be on for 8.5 minutes. In 24 hours, 204 minutes, or 3.4 hours.

    the kilowatt/hr price of electricity of course varies according to where you live and from whom you buy it.
    I'm allowing 35 cents per kwh.

    So, in one hour idling the machine will consume 370 watts. In 24 hours 8887 watts.

    Cost of electricity used is 12.95 cents per hour. In 24 hours $3.10.

    Power was measured with a digital clamp meter. Voltage is given by my grid solar inverter.
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    Senior Member level3ninja's Avatar
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    When you say Watts I assume you mean Watt/hrs?

  3. #3
    Senior Member robusto's Avatar
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    What else what I mean?

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    Quote Originally Posted by robusto View Post
    Not a controlled scientific experiment by any means, but for those completely in the dark about how much electricity is used to leave
    a machine on this may shed some light.

    The figures are to leave it idling. Actually brewing will alter the figures to take into account the pump etc but given the few coffees brewed daily shouldn't be much higher.

    Machine here is a Grimac Eclisse 2 group.
    Ambient temperature 18į
    Amps: 10.5
    Volts 249
    Power: 2614 watts

    Heating element on: at 0.6 bar
    Heating element off: at 0.8+ bar

    On time: 22 seconds
    off time 2 mins 13 secs

    Per minute power: 43.56 watts
    Per on cycle watts: 15.97 watts

    So every time the element comes on, for 22 seconds, it uses 15.97 watts

    In one hour, the machine will have cycled on/off 23.2 times. In 24 hours, 511 times.
    In one hour, the heater will be on for 8.5 minutes. In 24 hours, 204 minutes, or 3.4 hours.

    the kilowatt/hr price of electricity of course varies according to where you live and from whom you buy it.
    I'm allowing 35 cents per kwh.

    So, in one hour idling the machine will consume 370 watts. In 24 hours 8887 watts.

    Cost of electricity used is 12.95 cents per hour. In 24 hours $3.10.

    Power was measured with a digital clamp meter. Voltage is given by my grid solar inverter.
    G'day robusto

    ... and that is exactly why I gave all my commercial espresso machines the bullet. Large boiler machines consume huge amounts of power just heating up the boiler before you can get your first cuppa. Like my 2 group La Pavoni (which I should flog off) - 18 amps @ 240V for 35 minutes warmup, then it also pulls 18A for a minute or two for every shot. Like your machine the La Pav also cycles to keep the whole mass of water up to temp. It also needs a lot of maintenance to avoid the dreaded "boiler fish oil taste".

    So when I went to a 6910 (the earlier one) I went to a 90 second warmup at circa 10A (never bothered to measure it as it heats up so fast anyway) and I only heat the water I use plus a little in reserve (about 180ml in all). My "virtual power bills" (I went solar at about the same time) would probably have dropped from $450 down to $400. Even blind taste testing found the 6910 made slightly better coffee than the La Pav (probably because it also has preinfusion, unlike the La Pav). Now I am using a Decent DE1 which also only heats on demand and warms up in 3 to 4 minutes. The coffee flavour also has gone up a few more notches.

    Even when I was learning to make coffee in the '70's I realised the boilers were a poor way of making a cuppa - the small boilers are temperature unstable, whilst the bigger boilers are incredibly inefficient. Heating elements and (DE1) mixing valves are a much better solution.

    Needless to say, this CS'r is not going back to boilers anytime soon.

    TampIt

  5. #5
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    Robusto, thanks for posting some real life figures. Funny how we all read figures slightly differently, I had seen some inexpensive two group commercial levers and kept far away due to huge boilers for half a dozen coffees a day, expecting horror running costs. It actually surprised me how reasonable it was to run a two group unit like yours. 50 cents a day for four hours, seems reasonable for the performance you get. Of course for those on solar, just buy another panel when you get your two group!
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  6. #6
    Senior Member robusto's Avatar
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    In the overall scheme of things electricity costs for a coffee machine aren't all that high -- less than the cost of a cafe coffee if I left mine on 24 hours.

    In any case, we have solar panels which at 5 KW more than cover the power draw. When the sun shines that is!! (I'll do a separate post on solar).

    Incidentally, the machine's rated power is 3200 watts, but I disabled one of the boiler elements so it can run on a 10 amp timer.
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  7. #7
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    Electricity Costs

    Thanks for posting, although probably needs a bit of an edit to fix the units.

    First post makes a bit of a mess of where you are referring to instantaneous power draw (W) against energy consumption (Wh or kWh).

    I ran my Pro700 off a Wemo insight switch, which logs detailed energy consumption over time - very accurately.

    After startup it settles down to an average draw of 150W. This equates to an energy consumption of about 3.6kWh per day if left on for 24 hours.

    Now running a R91 which is likely using a little more due to the larger boilers but I havenít yet tested it.

    House has 5kW solar + a Powerwall, so the machine running costs are probably around 40c per day. (Forgone exports @12c per unit)

    Whatís a Nespresso pod cost? Iíll bet itís more than that.
    Last edited by herzog; 5th November 2019 at 04:08 PM.
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  8. #8
    Mal Dimal's Avatar
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    An easy way for people, who don't own electrical metering devices, is to calculate their machine's Duty Cycle, note the nameplate power consumption figure (or the rated power of the elements connected), then record the duration that the machine is turned 'On' for. It is good enough to use this method for most purposes...

    Using Robusto's observations above, the Duty Cycle is calculated by...
    Time On x 100 divided by (Time On + Time Off) = 14.19% Duty Cycle.

    Average energy consumption in KWH (Units) is then calculated by...
    Nameplate rated power (KW) x Time on (say 4 Hrs) x Duty Cycle (14.19%)
    Using Robusto's data above again = 1.484 KWH of energy consumed.
    Or, roughly 1.5 Units at your particular energy consumption costs, say $0.25/Unit = $0.375 in Total, for four hours use.

    Not a lot of money really and probably not worth most people's time to even worry about...

    Mal.

    P.S.
    The above does not take into account the energy used to heat up the boiler contents initially.

    Use this simplified formula to calculate the energy required to heat the water within the boiler.
    Please not, this calculation does not account for thermal losses or that energy required to heat the boiler itself and any connected thermally conductive pipework, etc...
    Input Energy (KWH) = (4.2 x Water Volume x (Desired Water Temperature - Initial Water Temperature)) Divided by 3,600
    ⸫ KWH = (4.2 x Lt x Td)/3,600
    Using Robusto's numbers again...
    KWH = (4.2 x 8 x (125-21))/3,600
    = 0.971 KWH


    Add this to the original result above and the total including initial warm-up is 2.455 KWH.
    Or, about $0.61 all up. Still could be considered an almost negligible amount.

    Mal.
    Last edited by Dimal; 6th November 2019 at 04:51 PM.
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    338
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    Robusto, I assume yours is a standard uninsulated boiler?

  10. #10
    Senior Member robusto's Avatar
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    Uninsulated 5 litre boiler, yes.
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  11. #11
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    Quote Originally Posted by robusto View Post
    Uninsulated 5 litre boiler, yes.
    Makes the costs seem even more reasonable
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  12. #12
    Mal Dimal's Avatar
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    Added some info for those espresso machine owners who need to know all about their machine's energy usage...

    Mal.
    Last edited by Dimal; 6th November 2019 at 11:14 PM.



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